38 COLLEMBOLA OF MINNESOTA 



the same may be said. Most of the Podurids love the dark 

 and are to be found beneath bark, moss, stones, etc., where there 

 is moisture, and some of them live about or upon the water. The 

 social instinct is often very apparent, and sometimes a colony 

 of Podura or Achorutes may be found to fairly blacken the snow 

 or water by thousands. We have four genera in the family, three 

 of which are represented in the state by one species each. 



KEY TO THE FAMILY PODURIDAE. 



1. a. Feet two-clawed. Two anal horns. Post-antennal or- 



gan present. Ocelli 16. Genus Achorutes, 38. 



b. Feet with a single claw. No post-aritennal organ. 2. 



2. a.- Anal horns present. Furcula short, not reaching to 



ventral tube. 3. 



b. Anal horns absent. Furcula reaching as far as ventral 

 tube, dentes much bowed. Body shortened. Ocelli 16. 



Genus Podura, 39. 



3. a. Three anal horns. Furcula extremely short and thick. 



Body robust. Ocelli 16. Genus Friesia, 40. 



b. Two anal horns. Furcula short but very slender. Body 

 slender, Ocelli 10. Genus Xenylla, 40. 



Genus Achorutes Templeton, Schaffer 1834. 



These insects are of a slightly flattened cylindrical form, 

 with strong legs and a heavy body. The four-jointed antenna? 

 are stout, and about as long as the head. Sometimes the third 

 and fourth antennal segments appear fused when seen from cer- 

 tain positions. Each eye-spot contains eight ocelli, and there is 

 present a post-antennal organ composed of about four or five 

 tubercles arranged in a ring. The prothorax can be seen dor- 

 sally, although quite short. In our species each tibia bears a 

 single clavate hair at its tip. The body is sparsely haired. Ven- 

 tral tube very short, the two halves of its end apposing when 

 closed. No extensible filaments. Abd. IV bears the short, 

 stout furcula, which consists of a very heavy manubrium, thick 

 dentes, usually tapering but little. On the ventral side of the 

 dentes are one or several long, straight hairs ; which are not, 

 however, clavate, as in some Sminthtiridae. The mucrones is 

 of various forms, more or less toothed at apex, and sometimes 



